The invention relates to methods for producing a heat exchanger tube bundle for heat exchangers of electrochemical energy accumulators. It also provides a pressure welding apparatus for carrying out a variant of the methods, a heat exchanger tube bundle obtainable according to the methods, a heat exchanger module with a heat exchanger tube bundle of this type, a heat exchanger with two or more heat exchanger modules of this type, an electrochemical energy accumulator with a heat exchanger of this type, and a use of an electrochemical energy accumulator of this type. The invention is industrially usable in the field of the production and use of electrochemical energy accumulators.
Modern electrochemical high-performance energy accumulators (for short: high-performance batteries), such as, for example, nickel metal hydride batteries and lithium ion batteries, not only require elaborate battery management, but also efficient temperature control of the individual electrochemical storage cells (for short: individual cells) in order to ensure as good a performance of the electrochemical energy accumulator as possible and to prevent damage thereto.
An electrochemical energy accumulator of this type is revealed in German patent document DE 10 2004 005 394 A1. The electrochemical energy accumulator has heat exchanger modules (called heat exchanger units there), between the heat exchanger tube bundles of which (called heat exchanger channels there) a plurality of individual cells can each be arranged next to one another in at least two adjacent rows. A temperature-control medium can flow through the heat exchanger modules, heat exchanger tube bundles and forward-flow distribution tubes and return collecting tubes (called flow distribution channels there) etc.
The heat exchanger tube bundles are usually produced from injection-molded plastic plates with a wavy profile, into which heat exchanger channels are milled. Adjacent heat exchanger channels are each separated from one another and from the surroundings by means of webs of material which is not removed during the milling operation. Two milled plates are then arranged one above the other, such that milled portion lies above milled portion, and web lies on web. The plates are subsequently joined together by laser welding in the region of the webs bearing against one another.
This method has several disadvantages. For example, injection-molded plastic plates can be integrated into series production only with difficulty. In addition, the milling of the wavy plastic plates is complicated and leads to a high reject rate which, under unfavorable circumstances, can amount to up to 40%. Furthermore, because of the wavy profile of the injection-molded plastic plates, laser welding is likewise complicated and prone to error. For example, even a slight deviation of the plastic plates from the ideal wave profile is sufficient to cause welding errors, which in turn cause the heat exchanger tubes to be loose in relation to one another or in relation to their surroundings. Furthermore, although the joined-together heat exchanger tube bundles are very stable in relation to inwardly directed compressive forces because of the webs which remain during the milling operation, they are, however, highly inflexible. As a result, heat exchanger tube bundles and individual cells have to be pressed against one another with a relatively high force in order to provide optimal heat-conductive (i.e., in particular gap-free or form-fitting) contact between heat exchanger tube bundle and individual cells.
One object of the present invention is to overcome the above-mentioned disadvantages of the prior art.
This and other objects and advantages are achieved by the method according to the invention for producing a heat exchanger tube bundle for heat exchangers of electrochemical energy accumulators, in which a plurality of electrochemical storage cells (for short: individual cells) are arranged next to one another in at least two adjacent rows. Heat exchanger tube bundles which fit closely against the individual cells in a form-fitting manner are arranged between the adjacent rows.
According to the invention, the method has the following steps:
a) two deep-drawable material strips, for example plates or blanks, are supplied;
b) at least the heat exchanger channel or the intended heat exchanger channels and the intended profile are incorporated into the material strips by deep drawing;
c) the forward-flow distribution apertures intended for the heat exchanger tube bundle are incorporated into a first material strip from step b), in order to obtain a first heat exchanger plate, and the return collecting apertures intended for the heat exchanger tube bundle are incorporated into a second material strip from step b), in order to obtain a second heat exchanger plate;
d) the first and the second heat exchanger plate from step c) are aligned in such a manner that the webs of the two heat exchanger plates border each other, and the heat exchanger channels form heat exchanger tubes, and the forward-flow distribution apertures and the return collecting apertures do not overlap; and
e) the arranged heat exchanger plates from step d) are joined together in order to form a heat exchanger tube bundle.
The method according to the invention is very rapid and operates with a reject rate of close to 0%. Furthermore, it can readily be integrated into series production by being designed, for example, as a continuous method in which the required material strips are obtained by cutting from rolls. Furthermore, it is highly flexible with regard to the profile which is to be incorporated into the material strips by deep drawing. Said profile has to be complementary to the geometric shape of the individual cells, the use of which is planned so as to ensure that the heat exchanger tube bundle produced can fit closely against the individual cells in as readily heat-conductive a manner as possible (i.e., in particular in a form-fitting manner and/or without gaps). Suitable individual cells can have a multiplicity of geometric shapes.
However, customary electrochemical individual cells, for example of the nickel metal hydride type, have a cylindrical form, and therefore, as a profile which is complementary thereto, in particular a wavy profile has to be incorporated into the material strips in step b).
In a second embodiment of the present invention, steps b) and c) are reversed. Accordingly, the alternative method has the steps that
a) two deep-drawable material strips are supplied;
b) the forward-flow distribution apertures intended for the heat exchanger tube bundle are incorporated into a first material strip, and return collecting apertures intended for the heat exchanger tube bundle are incorporated into a second material strip;
c) at least the heat exchanger channel or the intended heat exchanger channels and the intended profile are incorporated into the first material strip and the second material strip from step b) by deep drawing, in order to obtain a first and a second heat exchanger plate;
d) the first and the second heat exchanger plate from step c) are aligned in such a manner that the webs of the two heat exchanger plates border each other, and the heat exchanger channels form heat exchanger tubes, and the forward-flow distribution apertures and the return collecting apertures do not overlap; and
e) the arranged heat exchanger plates from step d) are joined together in order to form a heat exchanger tube bundle.
Whereas the first embodiment, has the advantage that only one type of material strip must be handled during the deep-drawing operation (step b)), the second embodiment has the advantage that only one type of material strip has to be handled during the incorporation of the apertures (step b)). Therefore, either the first embodiment or the second embodiment may be advantageous, depending on how the material strips must be processed.
The deep-drawable material strips for step a) of the method can preferably be obtained by cutting from rolls. As a result, the method can be particularly advantageously integrated into series production.
The channels, grooves and webs provided for the heat exchanger tube bundle can all be incorporated during the deep-drawing step of the method according to the invention. As a result, further method steps which complicate and delay the method and in which channels, grooves and webs which may otherwise be required would have to be incorporated, can be spared.
Furthermore, the forward-flow distribution apertures and the return collecting apertures can be incorporated by punching, with, preferably, further unnecessary or excess material additionally being removed from the material strips. This permits a particularly simple and rapid incorporation of apertures and preferably removal of excess material.
Furthermore, the method can be simplified and accelerated even further if the deep drawing and the punching are carried out in one step.
When the heat exchanger plates are joined together in step e), it is preferred if they are joined together in such a manner that the heat exchanger tubes are sealed in relation to one another and the heat exchanger tube bundle is sealed along its circumference in relation to the surroundings at least in a manner tight to temperature-control medium, i.e., tight in relation to the temperature-control medium. It is furthermore preferred if they are sealed fluid-tightly, (i.e., in relation to liquids and gases) in order to prevent a loss of temperature-control medium during operation and an associated deterioration in the temperature control.
The heat exchanger plates are joined together in step e) preferably by pressure welding. Heating element welding is especially desirable, particularly direct heating element welding. In comparison to laser welding, these welding variants have the advantage of being less complicated and error-prone for the workpieces (heat exchanger plates) with a wavy profile which are to be welded together here. For example, they tolerate a slight deviation in the wavy heat exchanger plates by said deviations being compensated for during closing of the pressure welding mold. As a result, welding errors scarcely occur, and therefore the heat exchanger tube bundles produced have no or at least virtually no leakages. Furthermore, such welding variants permit particularly rapid joining together of the two heat exchanger plates within a few seconds (preferably less than 20 s, in particular less than 5 s), which favors cost-effective series production of the heat exchanger tube bundle according to the invention.
The method according to the invention can furthermore be improved by joining the heat exchanger plates in step e) together by fully mechanical or automatic welding. As a result, the method can be simplified and accelerated even further.
A third aspect of the present invention provides a pressure welding apparatus for carrying out the above-described method. The apparatus is designed in such a manner that all of the welding seams for joining together two heat exchanger plates to form a heat exchanger tube bundle and for sealing the heat exchanger tubes in relation to one another and for sealing the heat exchanger tube bundle along its circumference in relation to the surroundings, can be produced in a single welding operation (for short: stroke).
As a result, the pressure welding apparatus according to the invention makes it possible to perform the method according to the invention particularly rapidly and efficiently, and favors the implementation thereof in the form of cost-effective series production.
A preferred embodiment of the pressure welding apparatus according to the invention has a male welding mold or a welding punch and a female welding mold, which can be moved toward each other to close the apparatus for a welding operation. The surface of the male welding mold and the surface of the female welding mold copy the profile of that surface of a joined-together heat exchanger tube bundle which faces them in each case or copy the profile such that the male welding mold and the female welding mold fit closely against the heat exchanger tube bundle and the closed state of the pressure welding apparatus. Furthermore, the male welding mold and/or the female welding mold has or have at least one heating element in the region which, in the closed state of the pressure welding apparatus, borders the welding seams of the heat exchanger tube bundle. With a pressure welding apparatus of this type, welding seams can be produced rapidly and precisely on profiled workpieces in a thermal manner. As a result, the method according to the invention can be carried out even more rapidly and more efficiently.
In another embodiment of the pressure welding apparatus, the male welding mold has welding webs which lie opposite welding webs of the female welding mold. The welding webs follow the profile of the heat exchanger tube bundle such that they fit closely on both sides against the welding seams of the heat exchanger tube unit in the closed state of the pressure welding apparatus. With the aid of the welding webs, the welding seams provided can be produced particularly rapidly, efficiently and precisely in a single stroke.
In this case, the at least one heating element is arranged on the welding webs of the male welding mold and/or the female welding mold (i.e., it is attached or incorporated, preferably to or on the insides of the welding webs). In particular, the at least one heating element is incorporated into the welding webs along the ends of the welding webs. This further improves the rapid, efficient and precise production of the welding webs provided.
The at least one heating element is preferably a heating resistor (in particular a strip heater or a heating wire), which follows the ends of the heating webs. In this case, the heating element is preferably coated with an inert plastic, in particular with polytetrafluoroethylene (for short: PTFE, for example Teflon from DuPont), so that the welding webs can easily be separated from the joined-together heat exchanger tube bundle when the pressure welding apparatus is opened.
A further aspect of the pressure welding apparatus according to the invention provides means for aligning two heat exchanger plates which are to be joined together, with the means being arranged between the male welding mold and the female welding mold. The two heat exchanger plates to be joined together can therefore be brought automatically into the correct position and arranged or oriented in relation to each other as intended before and/or during a pressure welding operation. This permits a further acceleration and simplification of the method according to the invention and therefore promotes the implementation thereof in the form of cost-effective series production.
The aligning means preferably comprise a basic body facing the female welding mold and a pressure plate facing the male welding mold, which pressure plates can be moved toward each other to close the apparatus for a welding operation (for short: stroke), with the surface of the basic body and the surface of the pressure plate copying the profile of that surface of a heat exchanger tube bundle which faces them in each case such that the basic body and the pressure plate fit closely against the heat exchanger tube bundle in the closed state of the pressure welding apparatus. Furthermore, the basic body has slots which lie opposite slots of the pressure plate; in the closed state of the pressure welding apparatus, the webs of the male welding mold reach through the slots of the pressure plate and the webs of the female welding mold reach through the slots of the basic body. The pressure plate centers the two heat exchanger plates to be joined together on the basic body with the aid of a defined, predetermined compressive force and therefore brings about an automatic arrangement of the two heat exchanger plates in the designated position with respect to each other. As a result, the method according to the invention can be simplified and accelerated even further.
The aligning provision can furthermore comprise at least one stop strip attached to the basic body, to serve as a stop for the two heat exchanger plates to be joined together. This permits an even more rapid and more precise arrangement of the two heat exchanger plates.
A further development of the pressure welding apparatus according to the invention has means for centering the pressure plate and the basic body when the apparatus is closed. More reliable and precise closing of the pressure welding apparatus can therefore be ensured, so that the pressure welding apparatus can be closed more rapidly with its component engaging one in another, and the method according to the invention can therefore be accelerated.
In this case, the centering means preferably comprise at least one centering bolt and one centering bore which interact in such a manner that the pressure plate and basic body are guided into the intended position when the apparatus is closed.
There can preferably be four centering bolts which are attached to or formed on the basic body, arranged in the corners of the basic body, and when the apparatus is closed, engage in four centering bores incorporated into the pressure plate.
In addition, the centering bolts can be designed in the manner of a spacer such that, in the closed apparatus, a predetermined distance is provided between pressure plate and basic body, into which a heat exchanger tube bundle according to the invention fits.
A fourth feature of the present invention provides a heat exchanger tube bundle which is obtainable according to the above-described method. According to the invention, the heat exchanger tube bundle is formed from a first deep-drawn heat exchanger plate and a second deep-drawn heat exchanger plate, of which each has at least two heat exchanger channels spaced apart from one another by means of webs. The two heat exchanger plates are aligned in such a manner that the heat exchanger channels lie opposite each other and the webs border each other. As a result, the heat exchanger channels of the first heat exchanger plate together with the opposite heat exchanger channels of the second heat exchanger plate form heat exchanger tubes that are spaced apart from one another by grooves formed by the webs and the channel walls bordering them. The heat exchanger tube bundle furthermore has a profile which is shaped so that it can fit closely against the individual cells in a form-fitting manner between adjacent rows of a plurality of electrochemical storage cells (for short: individual cells) which are arranged next to one another in at least two adjacent rows.
The heat exchanger tube bundle according to the invention has no, or almost no, leakages. Furthermore, it is more flexible than heat exchanger tube bundles comprising heat exchanger plates with milled heat exchanger channels, since it has a lower material thickness in the region of the webs between the heat exchanger tubes. As a result, a lower compressive force is required to press the heat exchanger tube bundle according to the invention in a gap-free manner (i.e., as heat-conductively as possible) against the individual cells to be temperature-controlled. When the heat exchanger tube bundle according to the invention is pressed on or fitted closely, less compressive force has to be used in order to produce a readily heat-conductive contact. Thus, there is also a lower risk of cross-sectional changes to the heat exchanger tubes, which could lead to the temperature control being impaired.
In this case, a heat exchanger tube of the heat exchanger tube bundle according to the invention is formed from the bases and the walls of the mutually opposite heat exchanger channels, with the walls extending between the bases and the webs and being aligned at an angle thereto. As a result, the heat exchanger tube bundle is even more flexible and can be pressed onto the individual cells or fitted closely against them with even less compressive force and in an even better heat-conducting manner.
In a first embodiment of the invention, the angle between a wall and the base of a heat exchanger channel and between the wall and the bordering web is 90°. This gives the individual heat exchanger tubes more stability in the region of their walls such that the heat exchanger tube bundle as a whole can absorb considerable compressive forces without cross-sectional changes occurring in the heat exchanger tubes.
In an alternative second embodiment, the angle between a wall and the base of a heat exchanger channel and between the wall and the bordering web is less than 90°, preferably 45 to 89°, and particularly preferably 60 to 75°). As a result, although the heat exchanger tubes have a lower degree of stability, the heat exchanger tube bundle has instead overall a higher degree of flexibility. Therefore, less compressive force needs be applied to press or fit individual cells and heat exchanger tube bundles against one another in a readily heat-conductive manner.
It is also possible for the angle in some heat exchanger channels to be 90° and in others to be less than 90°, with it also being possible for the deviation from 90° to be variable.
The heat exchanger plates are joined together in the region of the webs and in the region of their circumference preferably, in such a manner that the heat exchanger tubes are tightly sealed to temperature-control medium, preferably fluid-tightly. In relation to one another and with respect to the surroundings of the heat exchanger tube bundle in order, during operation, to prevent a loss of temperature-control medium and an associated deterioration in the temperature control.
The heat exchanger tube bundles are preferably formed from a deep-drawable plastic which is resistant to temperature-control medium. Materials of this type have the advantage of being easily available, easily processable, generally electrically insulating, low in weight (which is of great significance in particular for mobile applications, for example in a vehicle) and high in long-term durability.
In particular, aromatic polyesters, aromatic polysulfides or aromatic polyetherketones or mixtures thereof, preferably PET-G, PPS or PEEK or mixtures thereof, particularly preferably PET-G, have proven suitable materials in this case.
A fifth aspect of the present invention is the provision of a heat exchanger module, comprising a heat exchanger tube bundle as described above. According to the invention, the heat exchanger module has one or more pairs of adjacently arranged first and second heat exchanger tubes. Each heat exchanger tube, in the input region, has a forward-flow distribution aperture which is formed in the first heat exchanger plate, and in the output region, a return collecting aperture which is formed in the second heat exchanger plate. In this case, in adjacent heat exchanger tubes, the forward-flow distribution aperture of a first heat exchanger tube is in each case arranged next to the return collecting aperture of a second heat exchanger tube, and the forward-flow distribution aperture or return collecting aperture of the first heat exchanger tube is arranged diametrically to the forward-flow distribution aperture or return collecting aperture of the second heat exchanger tube. Thus, during correct operation, there is opposite fluid flow in adjacent heat exchanger tubes (for short: counterflow principle). Furthermore, the forward-flow distribution apertures of the first heat exchanger tubes are fluidically connected to a first forward-flow distribution tube, and the forward-flow distribution apertures of the second heat exchanger tubes are fluidically connected to a second forward-flow distribution tube, and the return collecting apertures of the first heat exchanger tubes are fluidically connected to a first return collecting tube, and the return collecting apertures of the second heat exchanger tubes are fluidically connected to a second return collecting tube. In addition, the forward-flow distribution and return collecting tubes have connecting means for supplying and removing a temperature-control medium.
The heat exchanger modules according to the invention can be combined in a simple manner to form heat exchangers. They can furthermore easily be fitted closely against individual cells in a readily heat-conductive manner on account of their profile and their flexibility and, on account of the counterflow principle implemented therein, ensure efficient, reliable and uniform cooling of the individual cells.
The heat exchanger module is configured such that it can be stacked, with intermediate spaces in which individual cells can be arranged in a form-fitting manner being provided between in each case two stacked heat exchanger modules. A particularly efficient and space-saving cooling of a relatively large number of individual cells can therefore be achieved.
In one embodiment, the connecting means for supplying and removing a temperature-control medium comprise means with which the forward-flow distribution tubes of a first heat exchanger module of a heat exchanger module stack can be fluidically connected to the return collecting tubes of an adjacent second heat exchanger module, while the return collecting tubes of the first heat exchanger module can be fluidically connected to the forward-flow distribution tubes of an adjacent third heat exchanger module. The final heat exchanger modules of a stack of heat exchanger modules can furthermore have connecting branches for supplying and removing temperature-control medium, which connecting branches are preferably attached in each case to a forward-flow distribution tube and return collecting tube. Particularly efficient distribution of the temperature-control medium, and particularly uniform temperature-control of the individual cells, can therefore be achieved.
The forward-flow distribution tubes of a first heat exchanger module in a heat exchanger module stack preferably bear against the return collecting tubes of an adjacent second heat exchanger module, with the forward-flow distribution tubes of the first heat exchanger module and the return collecting tubes of the adjacent second heat exchanger module having interacting adjusting aids. The adjusting aids facilitate the stacking of the heat exchanger modules.
The interacting adjusting aids are preferably a groove-pin combination, a forward-flow distribution tube of the heat exchanger module having a groove or a pin, and one return collecting tube of the adjacent second heat exchanger module having a pin interacting with the groove or a groove interacting with the pin. The pin can be provided in the form of a spring element, and the groove and pin can be joined together in a heat exchanger module with the aid of an adhesive, in order to improve the stability of the stack.
A sixth aspect of the present invention is a heat exchanger, comprising two or more heat exchanger modules as described above. According to the invention, the forward-flow distribution tubes of a first heat exchanger module are fluidically connected to the return collecting tubes of an adjacent second heat exchanger module and, if there are three or more heat exchanger modules, the return collecting tubes of the first heat exchanger module are fluidically connected to the forward-flow distribution tubes of an adjacent third heat exchanger module. Two of the heat exchanger modules are arranged at the ends and each close the stack, and therefore have only one adjacent heat exchanger module. The final heat exchanger modules have connecting means, which are designed as connecting branches or connecting flanges, for supplying and removing a temperature-control medium. The connecting means are each attached to a final forward-flow distribution tube or return collecting tube. Furthermore, intermediate spaces for receiving electrochemical storage cells (for short: individual cells) are provided between the heat exchanger tube bundles of adjacent heat exchanger modules.
Due to flexibility and the counterflow principle implemented therein, the heat exchangers according to the invention permit efficient, reliable and uniform cooling of the individual cells. Furthermore, they have a low weight, which is of great advantage in particular for mobile applications.
A seventh aspect of the present invention provides an electrochemical energy accumulator, comprising a heat exchanger as described above, which has two or more heat exchanger tube bundles as described above, and two or more electrochemical storage cells (for short: individual cells) which are arranged in a form-fitting manner in intermediate spaces between the two or more heat exchanger tube bundles. The individual cells are connected electrically in series by means of pole connectors, which are fastened to the individual cells by pole connector screws. According to the invention, the pole connector screws are supported by at least one disk spring, preferably by three disk springs.
During normal operation, the electrochemical energy accumulator according to the invention reliably supplies electric energy (even despite multiple vibrations and impacts), since the pole connector screws supported by disk springs do not work loose, even in the event of vibrations and impacts, but rather remain firmly seated and reliably maintain the electric contact.
An eighth aspect of the present invention is the use of the electrochemical energy accumulator as described above for the on-board power supply of a vehicle and/or for the power supply to a driving device of a vehicle.
The use according to the invention is therefore particularly advantageous because the electrochemical energy accumulator can easily be adapted to a wide spectrum of power requirements, for example by adding or taking away heat exchanger modules. Furthermore, it has a low weight and is insensitive to impacts and vibrations as customarily occur in the case of vehicles.
The vehicle can be in particular a road vehicle (passenger vehicle, truck, utility vehicles, tractor, coaches or the like) which have one or more types of drive (hybrid drive), of which one comprises an electric drive. Electric drives of this type require a high degree of power and dynamics and therefore efficient temperature control of the individual cells of its electrochemical energy accumulator, which can be ensured with the present invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
Only the features required for understanding the invention are denoted.